https://devzone.nordicsemi.com/f/nordic-q-a/73118/unable-to-connect-debugger-after-nrfjprog---recover-due-to-default-regout0I have a custom board with an nRF52840 that uses high-voltage mode (5V on VDDH) and the chips internal voltage regulators. This requires setting REGOUT0 to 3.3V. My firmware sets this correctly (along with both DC/DC enables) and the board works greaten-USTelligent Community 13Tue, 23 Mar 2021 13:58:44 GMThttps://devzone.nordicsemi.com/thread/301458?ContentTypeID=1Tue, 23 Mar 2021 13:58:44 GMT137ad170-7792-4731-bb38-c0d22fbe4515:2889711f-0d91-4a73-bf91-b8e1adbe9d43Vidar Berg<p>As Dimitry said, the default REGOUT0 setting should not get applied if you can avoid resetting the device before the --memwr command. </p> <p>Could you try using --erase instead of --recover, or is --recover needed to disable APPROTECT in your case?</p> <p>e.g.</p> <p style="padding-left:30px;">nrfjprog --erase</p> <p style="padding-left:30px;">nrfjprog --memwr UICR.REGOUT0 --val &lt;3V3 setting&gt;</p> <p style="padding-left:30px;">nrfjprog --reset</p> <p>Also, I&#39;m not sure why programming becomes more stable with the external supply. Standalone debuggers usually come with built-in level shifters so the IO voltage should not have been a problem. Is the VREF pin connected to Vdd on your target board?</p> <p><img src="https://devzone.nordicsemi.com/resized-image/__size/320x240/__key/communityserver-discussions-components-files/4/pastedimage1616508251137v1.png" alt=" " /></p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/301341?ContentTypeID=1Tue, 23 Mar 2021 08:44:13 GMT137ad170-7792-4731-bb38-c0d22fbe4515:3d0d758b-b7e0-4ae2-beff-d9112265965eDmitry<p>Hi,</p> <p>you can try to erase chip and then write UICR without device reset directly with jlink script, as explained <a href="https://devzone.nordicsemi.com/f/nordic-q-a/33911/what-are-the-raw-jlink-exe-commands-sent-by-nrfjprog-exe">here</a>.</p><div style="clear:both;"></div>